1. Field of the Invention
The present invention relates to the field of computer graphics and, in particular, to techniques for computing indirect lighting levels present within a computer-generated graphics scene.
2. Description of the Related Art
It is currently common for video games to pre-compute elements of direct or indirect lighting (or both) for a given set of three-dimensional (3D) scene geometry. The pre-computed lighting levels are then used to light elements of the scene geometry at runtime. Typically, pre-computation techniques may be used to render indirect lighting for the 3D scene geometry using an arbitrary direct lighting scenario. The indirect lighting is usually pre-computed for the 3D scene geometry, as the techniques currently employed lack the performance characteristics necessary for video games (i.e., they lack the performance characteristics for computing the indirect lighting in real-time for frames of computer-generated animation).
In practice, game designers and/or lighting artists specify lighting parameters for a scene, and the resulting lighting (both direct and indirect) may be pre-computed. For example, a lighting artist may specify a direct lighting scenario for the 3D geometry of a given scene. In turn, the lighting scenario is evaluated to derive what indirect lighting results from the direct lighting, based on the actual 3D geometry of the scene. While this approach for pre-computing direct/indirect lighting is capable of generating compelling results, the work flow for the lighting artist is somewhat less than ideal. For example, this approach often relies on overnight processing on large render farms to derive the indirect lighting results. Thus, in practice, a lighting artist may make changes to a given scene and then have to wait several hours before being able to observe and evaluate the results. Stated more generally, the process of pre-computing indirect lighting using direct-to-indirect transfer computations (and other pre-computed lighting techniques), generates accurate indirect lighting, but often suffers from long pre-compute times, large datasets and modest frame rates.